Permutation and combination is the most basic concept of combinatorics. The so-called arrangement refers to taking out a specified number of elements from a given number of elements for sorting. Combination refers to taking out only a specified number of elements from a given number of elements, regardless of sorting.

The central problem of permutation and combination is to study the total number of possible situations in a given permutation and combination. Permutation and combination are closely related to classical probability theory.

Development course:

Although mathematics began in ancient times, there was no skill because the development of social production level was still in the low stage.

With people's understanding and research on numbers, in the process of forming mathematical branches closely related to numbers, such as the formation and development of number theory, algebra, function theory and even functional, the diversity of numbers is gradually discovered from the diversity of numbers, and various counting skills are produced.

At the same time, people have a profound understanding and research on numbers. In the process of the formation and development of various mathematical branches closely related to shapes, such as geometry, topology and category theory, the diversity of numbers and shapes is gradually discovered from the diversity of shapes, and various skills of numbers and shapes are produced.

Modern set theory and mathematical logic reflect the potential combination of number and shape. However, modern algebraic topology and algebraic geometry closely link numbers with shapes. All these have had and will continue to have a far-reaching impact on the formation and development of modern combinatorics centered on digital skills.